This invention relates to illuminant-compensation mechanisms, and more specifically to methods and systems for an illuminant-compensation mechanism for operations on an image with a human face.
Image color (or image gray level) is very sensitive to variations in lighting, thus resulting in an image of an object appearing considerably different under different illuminations. Further, psychophysical experiments have shown that the human visual system has difficulty identifying images of the same face under considerably different illuminations (see, e.g., Y. Moses, S. Edelman, and S. Ullamn, “Generalization of Novel Images in Upright and Inverted Faces,” Perception, vol. 25, pp. 443–461, 1996). Likewise, computer vision systems have difficulty obtaining a high-level of classification accuracy if face samples in the training and testing sets have different lighting conditions.
Illuminant-compensation preprocessing systems have been used to reduce the differences resulting from illumination variations. Presently, most illumination-compensation algorithms use gray level values for the entire image or an oval region inside the image when correcting for lighting differences. However, problems can arise because current systems do not take effects of extreme lighting conditions on a person's hair or brow, background lighting conditions or heavy shadows into consideration during illuminant-compensation.
Accordingly, there is a need for improved methods and systems for illuminant compensation.